A simple method for the preparation of cis-dichloro(1,4,7-triazacyclononane)platinum(II), cis-Pt(tacn)Cl2 is presented, together with the results of screening the compound against the K-562 (leukemia) and SK-OV-3 (ovarian) human cancer cell lines. While the compound shows no activity against K-562 cells, there is evidence for some cytotoxicity against SK-OV-3. The compound is much less effective than cisplatin, and its limited solubility restricts the useable concentration range.